We just got confirmation of a devastating attack on American troops in Afghanistan thirteen Americans. Traveling in a NATO convoy were killed by a suicide bomber in Kabul the capital city. This morning ABC's Martha -- who has covered the US military for years on the phone with us with the very latest. Martha good morning -- -- I hesitate to say those words good morning is because it is not one at all can you take us through what happen in Kabul. Well again what was happening -- this convoy contained the spot this is almost like a regular bus route for NATO troops. On board mainly US forces. Thirteen. US troops killed in the attack on a -- Suicide bomber drove a vehicle into the but essentially people who -- Very badly burned. Along with -- thirteen US killed there were four US wounded I suspect badly. A Canadian and also Afghan police and some civilians who were standing around they believed. This suicide bombers specifically. Targeted this but now their armored buses -- called -- knows. Because of the arm -- armor but could not withstand the power of this very big suicide bomb. As our viewers -- -- -- the capital city it's supposed to be the most secure part of Afghanistan after this decade long war but there's been a lot of violence in Kabul lately. Insurgents are are clearly aiming at Koppel for one reason they get a lot of media attention they -- the suspect but how. -- attack and they target westerners they target American troops and that's harder to do. In math in some other places so they are clearly going towards this tactic of these spectacular attacks we have. An attempted attack on the embassy recently and military headquarters fortunately no one was injured no Americans were injured in those attacks. But they are upping the ante here. Martha Raddatz on a terrible morning like this where. Always happy to have somebody -- your expertise and experience covering the US military we really appreciate it thank you once again.

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